Compound bow design has evolved from an initial design featuring force draw processing modules in which a bowstring is wound or fed around two eccentric grooves in modules located at each tip of each limb of the bow. This construction provides significantly more energy storage than is possible with conventional longbows; while at the same time providing a tremendous advantage in low holding weight (letoff) at a full draw position of the bow. This design, which is still in use, permits both a sustained draw and controlled aiming. Since then, successful compound bow design has utilized this double eccentric module concept to produce the force draw curves now available and well-known to those skilled in the art. More recent bow design involves single cam bows in which a string feed groove is added to one double eccentric groove module, with the other module being replaced by an idler wheel. While a double eccentric groove module provides desired energy storage and letoff, the eccentric, swinging hinge action, produces a rough “jerk” to the bow during release. It is therefore desirable to provide a bow that is smoother, faster, quieter and more accurate than previous designs.
An optimal force draw curve rises, peaks, and falls consistently, without bumps or ripples. The result is a smoother draw with improved energy storage that produces faster speeds. A smoother release, greater accuracy, with less vibration and noise also result. Nock travel of the bow needs to be straight and level so all the energy in the limbs is transferred directly to the arrow to produce this greater speed and increased accuracy. The advantage of a compound bow over a longbow results from the use of limb tip modules and cables to regulate the energy storage developed when the limbs (which act as springs) are compressed. When a longbow is drawn, and as the limbs are increasingly compressed, the rate of resistance increases. That is, draw weight increases as draw length increases due to a progressively higher spring rate in the limbs as they are bent backward toward the archer as he draws the bow.